Disposable diapers of the type widely used today, such as those manufactured and sold by the assignee of this application, generally comprise a three layer composite structure including a liquid-permeable bodyside liner, a liquid-impermeable outer cover and a batt of absorbent material sandwiched between the liner and the outer cover. The diapers have front and rear panels joined together by a crotch section, and may be made in a rectangular or hour glass shape. The front and rear panels each have waist portions that encircle an infant's body and are overlapped and joined together to hold the diaper in place. In order to eliminate the need for pins or other mechanical fasteners to join the waist portions together, which would pose a danger to the infant, and so as to provide a complete garment that is ready for use without the need for additional fastening devices, disposable diapers have included pressure sensitive adhesive tabs as fastening means for securing the front and rear panels together about the waist of an infant.
At the inception of disposable diapers as commercial products, the most prevalent fastening means was a flexible tab attached to each corner of either the front or rear panel of the diaper (generally the rear panel) consisting of a strip of flexible material carrying a layer of pressure sensitive adhesive on one surface. An end portion of the tab was adhered to the outer surface of the panel and a free end portion extended beyond the side edge of the garment. The free end portion was covered with a release liner to protect the pressure sensitive adhesive. When the garment was ready to be applied, the release liner was removed from each fastening tab so as to expose the pressure sensitive adhesive along the free end portion of each tab, and the free end portion was then secured to the outer surface of the other panel of the diaper after the front and rear panels were overlapped.
The foregoing prior fastening system provided a convenient and secure system for fitting a disposable diaper about an infant and is still widely used today. However, it suffers the disadvantage of resulting in only a single-closure fastening system. The liquid impermeable outer cover of a disposable diaper is a plastic film, such as polyethylene or polypropylene, that of necessity is quite thin, such as only about one or two mils thick. The pressure sensitive adhesive used for the fastening tapes is generally an aggressive adhesive with good adhesion to the material of the outer cover in order to provide for secure fastening. When one attempts to remove the fastening tabs from a diaper after they have been secured in place, the outer cover of the body panel of the diaper to which the adhesive is secured can be ruptured or stretched or in any event damaged sufficiently to make reuse of the diaper undesirable. This, for example, prevents a person from checking the diaper after it has been on for awhile and refastening it if it has not been soiled.
To meet this latter problem of single closure adhesive tape fastening systems, there have more recently been developed adhesive fastening tape systems that enable two or more closures of the diaper. These constructions utilize pressure sensitive adhesive fastening tabs that have primary and secondary fastening tapes; the primary tape is used for the first closure of the diaper, and the secondary tape for the second and any subsequent closure of the diaper. A particularly useful structure for a refastenable tape system is that currently employed in commercial products made by the assignee of this application. Refastenable tape tabs are secured to each side of the rear panel of the diapers near the upper margin thereof. Each refastenable tab includes a secondary fastening tape having a first portion secured to the exterior of the outer cover of the diaper and a second portion extending beyond the side margin of the diaper, the outermost extremity of which has a finger tab; a release element adhered to the liner of the diaper and having a second surface which is releasable relative to pressure sensitive adhesive; a primary fastening tape having a first surface releasably joined to the adhesive of the secondary element and carrying pressure sensitive adhesive on its opposite surface, the outer extremity of which has a tab extending beyond the tab of the secondary element. During manufacture of the diaper, the primary tape is releasably joined to the exposed surface of the release element along the bodyside liner of the diaper, with the second or free end portion of the secondary tape folded over and releasably joined to the second surface of the primary tape. The first closure of the diaper is made by peeling away the primary fastening tape from the release element and joining the exposed adhesive thereof to the outer cover of the front panel of the diaper; removal of the primary fastening tape from the release element is facilitated by the finger tab of the primary element. The secondary fastening tape is positioned at the front of the diaper and overlies the primary tape that forms the initial closure. When it is desired to open the diaper, the secondary tape is peeled from the primary tape, which is easily accomplished since the adhesive layer of the secondary tape is releasably joined to the second surface of the primary tape; lifting the secondary tape from the primary tape also is facilitated by the finger tab at its outer end. The second closure of the diaper is thereafter made by adhering the pressure sensitive layer of the free end portion of the secondary tape to the exposed second surface of the primary tape or to a section of the outer cover of the diaper, as desired; the former method, when employed, enables several more refastenings of the diaper since removal of the secondary tape from the release surface of the primary tape does not rupture the outer layer of the diaper.
Multiple closure or refastenable tape systems for diapers and other disposable garments thus have two requirements that must be met for proper operation. Firstly, the adhesive member which is to form the initial closure, such as the primary fastening tape described above, must release dependably from the element to which it is secured when in a storage or closed position. Secondly, the adhesive member forming the initial closure must remain bonded to the adhesive layer of the member that is to be used for the second and subsequent closures of the garment firmly enough to provide a good initial closure.